A NAND flash memory is widely known as a semiconductor memory device that can store data in a non-volatile manner and provide high storage capacity. The NAND flash memory has a cell array that includes an arrangement of NAND cell units, each NAND cell unit including a plurality of memory cells connected in series.
The NAND flash memory reads data stored in the memory cell by determining whether a current flows from a bit line to a source line side via the NAND cell unit. In this case, a leak current may flow from the bit line to a well in which the NAND cell unit is formed, thus generating false reading during the read operation.